Non-polarized geophysical electrode

ABSTRACT

The non-polarized geophysical electrode has an electrically conductive metal disk mounted at its bottom opening. A mixture of an adhesive such as epoxy, inorganic binder, or RTV silicone, and fine particles in micron or nano size of graphene, nickel, nanotube, or graphite is applied on the outer bottom surface of the conductive metal disk. A lead wire of the electrode is connected to the inner surface of the conductive metal disk and extends outward through a liquid-tight strain relief mounted at a cap provided at the top of the housing of the electrode.

BACKGROUND OF THE INVENTION 1. Field of the invention

This invention relates to a geophysical electrode and more particularlyto a non-polarized geophysical electrode applicable for conductingmeasurements of geoelectric field signals in the ground to determineunderground composition in geophysical prospecting.

2. Background Art

Geophysical electrodes have been used for measuring telluric currentsignals, earthquake signals, and electrical potential from the earthground especially in various geophysical measurement methods such as MT(magnetotelluric), AMT (audio-magnetotelluric), IP (inducedpolarization), and resistivity measurement. In geophysical prospecting,a plurality of electrodes are employed for measuring and mapping theground potential signals in a geoelectric field at a selected groundsite. A plurality of electrodes are inserted into the ground at aplurality of selected locations of the site. The correlation of theground potential in geoelectric field signal measurements obtained atthose locations enables a determination of the mineral deposit at thesite. Presently, non-polarized electrodes are employed for carrying outthe measurements. Such electrode generally consists of a tubularenclosure having a porous bottom cover plate or alternatively having aporous tubular container mounted at its lower end. Commonly, porousceramic or gypsum is used for making the cover plate or the lowertubular container. The electrode is filled with an electrolyteconsisting of a chemical reaction compound such as copper sulfate(CuSO₄) or lead chloride (PbCl₂) solution. A copper (Cu) or lead (Pb)rod located inside the electrode extends from a lead wire terminalprovided at the upper cover of the enclosure to the bottom of thechemical electrolyte within the electrode.

In application, it is necessary to dampen the ground of a prospectingsite with an electrolytic compound solution such as a solution of sodiumchloride, then a plurality of the measuring electrodes are inserted intothe wetted ground at various selected locations of the site to measurethe geoelectric field signals at those locations. With the insertion ofthe porous lower portion of the electrode into the ground, the chemicalreaction compound of electrolyte in the electrode would inherently leachfrom the electrodes into the ground through the porous lower portionthus causing undesirable environmental pollution. The leaching of theelectrolytic compound into the ground would also deplete the amount ofthe electrolytic compound within the electrode with each use of theelectrode and therefore invariably reducing useful life of theelectrode. Additionally, the amount of electrolyte can moreover bedepleted by evaporation through the porous portion of the electrodehousing. Furthermore, the effectiveness of the electrode is greatlyreduced in cold weather condition when air temperature is lower than−10° C. causing freezing of its fluidic electrolyte.

In order to prevent the evaporation of the electrolyte from the porouslower plate or lower tubular portion of the electrode housing, it is anecessary to cover the electrode with a wet covering pad or wrappingmaterial during storage, which is messy to carry out.

Moreover, the effective contact surface between the electrode and theground is also restricted by the small size and diameter of the tubularporous portion of the electrode housing.

Still furthermore, such electrode filled with reaction chemicalelectrolytic solution is difficult to handle and transport withoutcausing leakage of the chemical compound in such circumstances, and itis also hazardous to the health of the workers fabricating the electrodedue to the inherent exposure of the workers to the toxic copper sulfateor the lead in the lead chloride of the chemical reaction compound inthe electrolyte.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide anon-polarized electrode which does not contain any chemical reactioncompound.

It is another object of the present invention to provide a non-polarizedelectrode which is easy to fabricate and use.

It is still another object of the present invention to provide anon-polarized electrode which does not cause any pollution to the groundand environment in its application.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will becomeapparent from the following detailed description of the preferredembodiments thereof in connection with the accompanying drawings inwhich

FIG. 1 is the perspective top and side and elevation view of theelectrode according to the present invention.

FIG. 2 is an exploded perspective side and bottom elevation view thereofshowing its various components.

FIG. 3 is a sectional side view of the electrode according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, the geophysical electrode 10 accordingto the present invention has an inverted funnel-shaped main housing 11having a round-shaped lower portion 12, an upwardly convergentdome-shaped middle portion 13 extending upwardly from the lower portion12 to an upper round neck portion 14. The diameter of the lower portion12 is larger than the upper round neck portion 14. Typically, theoverall height of the main housing 11 is about 10 cm; the diameter ofthe lower portion 12 is about 10 cm; and the diameter of the upper roundneck portion 14 is about 5 cm. The lower portion 12 has a bottom opening15. A round cap 16 is mounted on the upper round neck portion 14 tocover the upper opening of the main housing 11. The main housing 11 andthe round cap 16 may be made of a plastic material having an operatingtemperature range of −25° C. to 60° C. suitable for operating in variousextremely cold or hot weather conditions in geophysical prospectingsites.

It will be understood that although a cross sectional round shapehousing is shown as an exemplary embodiment, it may also be of othershapes such as square, or multi-angular cross sectional shape to providethe same purposes.

A metal disk 17 made of a high electrically conductive metal such ascopper is mounted in the lower portion 12 and located immediatelyadjacent to the lower opening 15. The metal disk 17 is maintained inplace by a supporting disk 18 butting against the inner surface of themetal disk 17. The supporting disk 18 is preferably made of anelectrically insulated material.

An electrical lead wire 19, extending from the top of the electrode 10within the main housing 11 and through an opening 20 in the supportingdisk 18, is connected to the upper surface 21 of the metal disk 17. Thelead wire 19 is secured safely to the round cap 16 by a liquid-tightstrain relief 22. The lead wire 19 is for connecting the electrode 10 tothe electrical potential measuring instrument.

A coating 23 of an electrically conductive material is applied on theouter bottom surface 24 of the metal disk 17. The conductive materialconsists of a mixture of micron or nano size fine particles of flakes orpowder of graphene, nanotube, nickel, or graphite, mixed with anadhesive material such as epoxy, inorganic binder, or RTV silicone. Themixture forms a dry coating 23 having a preferable thickness in therange of 0.3 mm to 1.0 mm on the outer bottom surface 24 of the metaldisk 17.

In use the electrode 10 can be simply placed on the ground of theselected prospecting site with the coating 23 in contact with the groundwhich has been pre-wetted with water rather than the necessity ofwetting the ground with environment polluting chemical electrolyticsolution as in using the known electrodes. The inverted funnel-shapedhousing 11 with the relatively larger lower portion 12 facilitates theelectrode 10 to position securely on the ground. Any polarizingpotential between the micron or nano size flakes of electricallyconductive substance and the metal disk 17 would be discharged by ohmiccontact among the flakes of electrically conductive substance as well asbetween the flakes of electrically conductive substance and the metaldisk 17, and the metal disk 17 per se does not retain any polarizingpotential.

The electrode 10 is maintenance free and has a rugged structure, safe tohandle, easy to use, and no harmful substance is released into theground in use since no health hazardous or toxic substance or compoundis used in its construction.

What is claimed is:
 1. A non-polarized geophysical electrode comprising:a hollow housing having a bottom opening, an electrically conductivemetal disk mounted in said housing and said disk having an outer bottomsurface located immediately adjacent to and covering said bottomopening, a dry coating of a mixture of fine particles of an electricallyconductive substance with an adhesive material applied on said outerbottom surface of said conductive disk, a lead wire connected to aninner surface of said conductive disk and extending outward from anupper end of said housing.
 2. A non-polarized geophysical electrodeaccording to claim 1 including a supporting disk mounted in said housingand located in contact with said inner surface of said conductive metaldisk for maintaining said conductive metal disk in a securely fixedposition within said housing.
 3. A non-polarized geophysical electrodeaccording to claim 2 wherein said housing has a funnel shape with around lower portion and a round upper end portion, said lower portionbeing larger in diameter than the diameter of said round upper endportion.
 4. A non-polarized geophysical electrode according to claim 2wherein said fine particles of electrically conductive substancecomprises of micron size graphene.
 5. A non-polarized geophysicalelectrode according to claim 2 wherein said fine particles ofelectrically conductive substance comprises of nano size grapheneflakes.
 6. A non-polarized geophysical electrode according to claim 5wherein said adhesive material is epoxy.
 7. A non-polarized geophysicalelectrode according claim 5 wherein said adhesive material is RTVsilicone.
 8. A non-polarized geophysical electrode comprising: a plasticinverted funnel-shaped housing having a round lower portion and a roundupper portion, said lower portion having a larger diameter than saidround upper portion, and said lower portion having a bottom opening, around cap secured on top of said round upper portion, an electricallyconductive metal disk mounted in said round lower portion of saidhousing, said metal disk having an outer bottom surface locatedimmediately adjacent to and covering said bottom opening of said lowerportion of said housing, a dry coating of a mixture of fine particles offlakes of an electrically conductive substance with an adhesive, appliedon said outer bottom surface of said metal disk, an electrical lead wireconnected to an inner surface of said metal disk and extending upwardfrom a top of said housing, said lead wire being secured to said roundcap with a liquid-tight strain relief.
 9. A non-polarized geophysicalelectrode according to claim 8 wherein said electrically conductivesubstance is chosen from the group of substance consisting of graphene,nanotube, nickel, and graphite, and said adhesive is chosen from thegroup of adhesive consisting of: epoxy, inorganic binder, and RTVsilicone.
 10. A non-polarized geophysical electrode according to claim 9wherein said flakes of electrically conductive substance are in micronsize.
 11. A non-polarized geophysical electrode according to claim 9wherein said flakes of electrically conductive substance are in nanosize.